1. Field of the Invention
This invention relates to a floating deposit removal system for removing deposits from an underwater structure. Typical underwater structures to which the invention is applicable include vertical, perpendicular and angular piles made of steel, concrete or other materials, including H-shaped piles, steel pipes, horizontal rods, legs of piers or of other structures, piles of offshore structures such as sea berths, artificial islands or the like, banks and bottoms of ships.
2. Description of Related Art
In the maintenance of such underwater structures, deposits such as shells, seaweed, rust, or sludge have been removed from the surfaces of the structures by human power with a chaplet rod or wire brush.
However, there are hundreds to thousands of such structures for which deposit removal is performed at sea. The time available for deposit removal is limited because of tides and weather conditions. Moreover, numerous workers and divers are required. Thus, the need for deposit removal from fixed underwater structures is an important factor contributing to high construction costs, instability in construction scheduling, and serious safety concerns. The need for underwater deposit removal gives rise to similar cost, scheduling and safety problems in the building and maintenance of ships.
Various efforts are made to prevent deposits, particularly marine organisms such as shells and seaweed, from easily attaching themselves to an underwater structure or the bottom of a ship. For example, special paints are frequently applied. However, it is impossible to prevent the attachment of deposits completely. Therefore, it is necessary to remove the deposits from time to time.
Devices for solving these problems are described in Japanese Utility Model Publication No. 60-15786 and Japanese laid-open Utility Model Application No. 56-138932).
The first of the above-mentioned Japanese publications discloses a device comprising a divisible cylindrical floating body and an annular frame secured to a support extending downward from the floating body. An edged portion is provided on the inner periphery of the floating body and/or on the frame so that, when the floating body and frame are installed on a steel-pipe pile, the tide and waves cause the floating body to travel vertically, and the edged portions slide on the pile to scrape away deposits from its surface.
The second of the above-mentioned Japanese publications discloses a device comprising an annular body installed onto a pile or the like of an offshore structure and having an internal space and an opening at the bottom of the body communicating with the internal space. A wing is provided on the outer periphery of the annular body, and a grinding and cleaning material is provided on the inside of the annular body. A gas spouting hole at the bottom of the pile releases gas, which fills the internal space, causing the body to rise on the pile due to increased buoyancy. The internal space within the body then fills with water, the body falls under its own weight while the wing supplies rotating torque. As this action occurs, the grinding and cleaning material cleans the surface of the pile.
The prior art devices disclosed in these two publications are able to remove deposits from a vertical pile. However, their effectiveness is limited because the movement of removal member (the edged portion of the first device or the grinding and cleaning material of the second) is dependent upon tides, waves, or the weight and buoyancy of a floating body. Moreover, such devices are not suitable for use in connection with slanted piles.